Two Zero Two Pole Active Compensation Replaces a Charge Pump

33 Pages·2008·0.66 MB·English

Mixed Signal Products
Two Zero Two Pole Active Compensation
Replaces a Charge Pump and Regulator
in PLLs 6-25-08
Stanley J. Goldman
Texas Instruments
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6/28/2008 Page 1
Mixed Signal Products
Agenda
(cid:127) PLL Review
(cid:127) Various Loop Filters
(cid:127) 2 Zero 2 Pole Plots and Equations
(cid:127) 2 Zero 2 Pole Results
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Mixed Signal Products
PLL Basic Block Diagram
Input Phase Transduced to Voltage and
Voltage Transduced to Output Phase
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Mixed Signal Products
Ideal VCO Transfer Function,
Transduces Voltage to Frequency (Edges)
ω =ω +K V
out off v tune
ω =∆θ /∆t
out out
T = 2 M T
o d
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Mixed Signal Products
Digital Phase Detector Timing and Response to Ramped VCO Phase
VDD D Q UP
RIN
C Q
CL
VDD D Q DOWN
VCOIN
C Q
CL
Reset
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Mixed Signal Products
Ideal Phase Detector Transfer Function,
Transduces Frequency (Edge) Differences to Voltage
θ
Vpd =K (5MHz Ref. Freq.)
avg d e
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Mixed Signal Products
Charge Pump Output Transduces Frequency (Edge) Differences
to Current, Kp=I/(2 π)
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Mixed Signal Products
Example of Lock, Digital Loop
(In Phase)
n 1
I

.
f
e
R 0
t
u
p
t 1
u
O

O 0
C
V
1
p
U
0
n 1
w
o
D 0
3
e
g
a 2
t
ol
V

e
n 1
u
T
0
0 50000 100000 150000 200000 250000
Time (ns)
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Loop Classifications
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Mixed Signal Products
Comparison of PLL Loop Filters
with Regulators driving VCO
(cid:127) Charge pump PLL
(cid:127) Replica Bias PLL
(cid:127) Digital PLL
(cid:127) 1 Zero Active PLL
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